The invention relates to the assembly of mining screens and particularly to the assembly of such screens which are provided with a plastic surface for enhancing the abrasion resistance of the screen as compared to stainless steel screens in severely abrasive mining applications such as grading or dewatering. Patents relating to such screens wherein elastomeric material is molded include U.S. Pat. Nos. 3,428,184; 3,483,976; 3,557,276; 3,900,628; 3,980,555; 4,062,796; and 4,100,248. Patent 4,120,785 discloses a screen formed from melt bonded transverse layers of elongated urethane, plastic or elastomeric rope members which have a tensile core. The tensile core portions of the rope members in one layer have a high elongation at break and are preferably formed of twisted strands of fiber or metal while the tensile core portions of the rope members defining the adjacent layer have a low elongation at break.
Some cylindrical plastic well screens are made by wrapping a plastic wire in a helical fashion around a plurality of longitudinal support rods with ultrasonic welds being made at each intersection in a fashion somewhat similar to that used for resistance welding metal well screens as disclosed in E. E. Johnson U.S. Pat. Nos. 2,046,457 and 2,046,458. Such cylindrical screens can then be cut longitudinally and flattened where flat panels are required. A metal screen can be coated with plastic but such a technique is generally used to provide corrosion resistance to the metal since a coating thick enough to provide any substantial degree of abrasion resistance would prevent careful control of slot width and of the shape of the surface profile.
Some plastic screen panels are molded solely of urethane and require a substantial amount of material for backing up the working surface. Other plastic panels are made using ultrasonic welds or solvent welds but such techniques are not satisfactory for use with urethane. It is known, however, that urethane can be thermally welded by heating it sufficiently to cause a partial melting to take place.